Again, this event is open to all! Lots of RF stuff will be happening. If at all curious, please come out and check out the festivities. Amateur radio. Amateur radio digital modes. Satellite communication. FOOD. SDR radio. Mesh networking and more.

Standford University is at it again with another round of free (as in beer) courses! This time they’re joined by the likes of Princeton, Penn, and the University of Michigan!

Why should you care? Well, Hive76 is forming a study group to help individuals tackle this incredible and challenging opportunity to be found within Standford’s Machine Learning course, of course! Our first meeting will be held tomorrow night during Open House Hours (7-11 PM)! If you are interested in taking this course, please take the time to register with Stanford at the link provided here.

Folks considering this course should be familiar with programming concepts and linear algebra, for sure! Recommended linear algebra lectures can be found here, and for your open source alternative to MATLAB, check out GNU’s Octave.

I was surprised at the absence of a concise illustration of magnetic dip available on the internet, so I cobbled together a short 3D animation using the excellent free software Blender. Magnetic dip is a very simple phenomenon but one which can quickly get confusing since it deals with 3-dimensional fields through space that can be difficult to visualize. The gist of it is that the Earth’s magnetic field lines are only parallel with the ground around the equator, and everywhere else the field lines actually dive downwards into the Earth by some angle, the steepest of which are found at the magnetic North and South poles. In the Philly area this angle is surprisingly steep, about 67 degrees below the horizontal — it’s actually more vertical than horizontal! This means that in areas far from the equator, tilting to the East or West will result in a compass error since the needle can align more closely with the magnetic field by deviating from the projection of the field lines onto the ground, which is what we normally think of as North. Tilt to the West in the Northern hemisphere, and the compass needle will tilt to the West as well.

It gets even more confusing when you are talking about traditional non-gyro-stabilized compasses, such as those normally found in small aircraft. The compass needle is usually weighted carefully such that it rests level with the ground under normal circumstances, but this means that when you accelerate in certain directions, that weight’s inertia keeps it lagging behind somewhat, resulting in yet more compass errors. These acceleration effects are not directly the result of magnetic dip, but they are partly the result of an incomplete attempt to deal with magnetic dip. Normally pilots are just taught to remember that this happens and vaguely what to do about it, but if you level out and stop accelerating the problem takes care of itself.

Blender allowed me to put this simple animation together in a very short time. It has a challenging learning curve, but it is a very powerful set of tools. Hopefully this animation will be useful to somebody out there other than me.

We are proud to welcome Lea Rosen, Rutgers-Camden law student, researcher, and writer, to Hive76 to present a talk entitled, “Hacking Your Lawyer: A Primer.”

“Ever feel like your questions elicit boring and disappointing answers from lawyers? It happens all the time, and it feels counterintuitive – the stuff you are working on is complex and exciting, and you know the law is complex and kind of interesting. Your gut’s not wrong – your questions are. I’ll explain why we talk the way we do, and how you can learn a couple simple lessons to help frame your questions in a way that will draw out the information you really want. “

In addition to her main presentation, she will also be discussing some of the topics that were brought up on our mailing list, like the legal implications of hacking the things that you own. There happens to be a DMCA Rulemaking Session this year, so she will discuss how the DMCA works and what it takes to get legal protection for hardware hacking. There will be a Q&A section afterwards because I’m sure we’ll have some questions. 🙂

A little more about Lea:

Her big motivation is to break down the cultural boundaries between technologists, hackers, lawyers, human rights advocates, activists, and theorists. She provides research assistance for Evgeny Morozov, author of The Net Delusion, and Greg Lastowka, Professor at Rutgers School of Law, Camden and author of Virtual Justice[pdf]. She has interned at the Electronic Frontier Foundation and in the Federal District Court in Newark, NJ. She volunteers with the Philadelphia ACLU and the National Lawyers Guild AnoNLG project, and she co-founded of the Rutgers Cyberlaw Society. She has written on the interpretation of software licenses by the 9th Circuit, encryption and border searches, and the privacy and liberty implications of domestic UAV deployment. She also had the opportunity to write an FAQ for the Yes Men! She has her BA in Humanities and will be getting her JD this May from Rutgers-Camden.

See you tonight!

UPDATE: Lea has informed me that Greg Lastowka’s book, Virtual Justice is available for free here[pdf]. It was released under a Creative Commons license! Nice! Hard copy available from Yale University press here.

Ok, you probably can’t make the baby grand in this picture, and even the metronome is likely to be a serious DIY challenge — but you can definitely make a pretty accurate DIY scale, and you can do it cheaply and easily.

I needed an accurate scale for a science project and knocked this baby together (based on this design) using found parts. I was able to easily measure to centi-gram precision and with a little care, a scale like this could be tuned to measure to milligram precision.

Precision (the ability to discriminate between differences in mass) is largely a matter of careful construction — accuracy (the ability to weigh to an agreed upon standard) is another matter altogether, and it basically hinges on having an accurate reference. Fortunately, a great institution, born of Philly — the U.S. Mint — was wise enough to make Nickels and Pennies in rather convenient dimensions. It turns out that nickels are 5.000 grams and pennies are 2.500 grams — so you not only have sub-milligram accurate references of convenient size — you also have an easy way to cross-check your scale by using nickels to weigh pennies and vice-versa.

Details of DIY Scale

The zoomed in photo shows most of the essential elements of construction. Basically, I used a threaded 10-24 rod for the balance (10-32 would have been a better choice). I used a wall-board razor as my knife-edge pivot point. Two angle-brackets served as a hard, flat surface for the knife edge. A nickel with a hole in it and some thread served as a reference weight (I wound up with a whole array of perforated nickels and pennies). A wall-board T-square served to measure the distance from the pivot to the reference weight. I used an index card and a small mirror to make a sliding mirror in order to read the position of the weight w/o parallax error. The whole shootin’-match was held on a stand that was salvaged from a cheap drill-press. Measurements were performed by reading the distance between the movable weight and the pivot point, and entering that value in a Google Docs spreadsheet.

I definitely could have purchased a milligram scale for far less than this cost me in terms of spare time, but I learned a lot about scales in the process. Almost all of it was stuff that I knew “in principle” — but actually building the scale infused my arm-chair knowledge with real-world experience, yielding an alloy whose properties seem to have exceeded its constituent parts.

The scale was nowhere near large enough to measure my satisfaction, but I estimate that this exercise yielded just about one metric ton of fun.

If you are at all interested in cognitive science, some theory behind it, or machine learning, I strongly urge you not to miss this! This will be geared towards folks without math backgrounds, and Josh will stick around to answer questions.

Welcome to Hive76

We are a hackerspace in South Philadelphia, at 1901 S 9th St. We are a group of hackers, DIYers, and Makers that tear things apart and put them
together in new ways. Please join our announcement list, discussion
list, or RSS feed to keep up to date on our exciting projects and events, or just email us at Hive76@gmail.com. And be sure to stop by our open house every Wednesday night!

Donations

Feel free to donate to Hive76 to bring science and technology to the local Philadelphia community and keep our doors open.